I am 36 weeks pregnant and I have Juvenile Diabetes. I am very lucky because i see my doctors and speak with my diabetic educators and nurses every week. And although I am in close contact with them, I still worry a lot and I have good days with glucose control and bad days with glucose control. I have gone low quite a bit during this pregnancy and most of it has to do with the fact that I work on my feet and I am very sensitive to physical activity of any kind; but also sometimes to do with not knowing how many carbs are in the food i ate and not gauging my insulin correctly.
It is dangerous to go low even when you are not pregnant, which i am sure you know already, but it is more worrisome when you have a little one inside of you that is depending on proper glucose levels to grow big and strong. The baby gets it's glucose directly from you (the placenta and umbilical cord) and this helps the baby grow. If your glucose level is too high, this causes the baby to store the extra glucose in fat cells and leads to the baby being quite large by the time the baby is delivered. This is harmful because the lungs are not given the space they need to develop properly. Also if the baby is used to high blood sugar, then the baby's pancreas is used to having to produce extra insulin to try and break it down, This means that when he/she is born, they will have A LOT of insulin production and a lot less glucose to break down and this causes severe hypoglycemia in the baby. This can be treated, but it is dangerous because if the baby is sick while his sugar is still low, it can cause brain damage and learning disabilities.
Now, if you have low blood sugar levels in pregnancy it is considered even more scary. This is because, just like you, if the baby has low blood sugar, it puts the baby's body in a state of shock and causes brain damage and even a comatose state. The baby can not grow as it needs to because there is not even glucose in the baby's system to allow this. Also it does not allow for proper development of the brain to begin with because the brain runs completely on glucose and if there is no glucose, then that means there is no chance for the brain to prosper.
So does all of this mean you are going to have a baby that has brain damage and will be slow at reading because you had a bad night? No. Absolutely not. You did the right thing and the best thing for you and your baby. All you can do is treat the hypoglycemia as quickly as possible and try to prevent it from happening. I always make sure I have plenty of protein in my meals because this helps the carbohydrate to stay in your body longer and prevents lows. But like I said, I have had many days of troublesome occurrences and so far, my baby is right along the normal lines of any other fetus at this time in my pregnancy. My advice to you is to try to not worry. I have been so worried this whole time and I am just now starting to realize that I tried my best and that is all you can do. Keep an eye on three day patterns of your glucose levels going up and down, then adjust you insulin to that pattern. Most women have a period of a month where they do not need much insulin at all (usually 3rd and 4th month) and then it spikes back up. By the time you deliver, most women will have tripled the insulin amount they need from the time before they were pregnant. I used to need 8 units a meal and now I am at 22-24. And at bed I have to take 40-42 humalin N. So if you are not comfortable in adjusting your insulin amounts yet, you definitely will be by the time you are done having that baby!
So please, try not to worry too much. Yes it is dangerous for highs and more-so lows, but if you giver it your undivided attention and treat the highs and lows as soon as you notice it, you will be just fine. Most of the damage will only occur if you leave yourself untreated for a long time. Good luck and I know you and your baby will be just fine. The fact that you are so concerned means you care enough to take care of yourself. That is more that some mothers would do.